Each time you take a step or a vehicle changes speed or direction, it is experiencing acceleration. Acceleration is the rate of change of velocity over time and can be calculated as the change in velocity divided by the time elapsed. For example, a car accelerating from 60 mph to 90 mph in 3 seconds has an acceleration of 10 mph/s. Acceleration can be positive, like the car speeding up, or negative, like when braking and slowing down. Over time, the constant acceleration due to gravity causes objects in free fall to increase their velocity, gaining 10 m/s every second until air resistance balances the downward force.

1. Acceleration

2. Change in Velocity Each time you take a step you are changing the velocity of your body. You are probably most familiar with the velocity changes of a moving bus or car. The rate at which velocity (speed or direction) changes occur is called acceleration.

3. Acceleration= final velocity- starting velocity time Change in velocity = final – starting velocity velocity Acceleration= change in velocity time

4. A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is the car’s acceleration? Velocity(final) - Velocity(original) = Acceleration time 90 mph - 60 mph = 3 seconds 30 mph = 3 seconds = 10 mph/second

5. Positive acceleration Negative acceleration

6. A car traveling at 60 mph slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is the car’s acceleration? Velocity(final) - Velocity(original) = Acceleration time 0 mph - 60 mph = 6 seconds - 60 mph = 6 seconds = - 10 miles per hour per second

7. - A constant acceleration produces a straight line or linear slope (rise/run). - The slope of a non-linear velocity-time graph (rise/run) will predict an objects instantaneous acceleration. a = v/t

8. Free fall The constant acceleration of an object moving only under the force of gravity is "g". The acceleration caused by gravity is 10 m/s2 If there was no air, all objects would fall at the same speed Doesn’t depend on mass After 1 second falling at 10 m/s After 2 seconds 20 m/s 3 seconds 30 m/s

9. Falling Air resistance will increase as it falls faster An upward force on the object Eventually gravity will balance with air resistance Reaches terminal velocity - highest speed reached by a falling object.

11. until the force is equal

12. Equal forces, no acceleration